The next time you’re shopping for replacement tires, you might be surprised when you’re told your vehicle needs tires with a speed rating that’s way beyond any posted speed limits you’ve ever heard of. So why would you have to buy a tire that can go 186 mph (speed rating: Y) when you’ll never drive that fast without getting arrested or killed?

Even if you own a family sedan, like a Toyota Camry, you still might need V-rated tires, which means they have a speed rating of 149 mph? You’ll never drive that fast to the grocery store, so what’s the point?

A Misnomer

The confusion stems from the fact that speed ratings have nothing to do with how fast you actually drive. The term is a bit of a misnomer, but a recent conversation I had with Ian McKenney, Senior Product Manager at Bridgestone, sheds some light on where the speed rating idea comes from, and why it’s important for you to consider speed ratings when buying a new tire.

McKenney explained that speed ratings are determined by tests that tires have to pass at those specific speeds. So when a tire has a V rating, for example, that means it was actually tested in a lab at 149 mph.

Getting back to our Toyota Camry example where we need tires with a V speed rating, McKenney explained that those tires were actually tested by a lab on a high-speed drum, where they were forced to run in a controlled environment at 149 mph for a set period of time to make sure they wouldn’t overheat or lose their integrity and fall apart.

When they pass the test, they get a “V” stamped on their sidewall, which tells you that you could theoretically drive at those speeds without worrying about your tires overheating or the centrifugal force tearing that tire apart. In the real world, however, McKenney doesn’t recommend doing so.

Manufacturer Specs

Now that we understand how tires qualify for a certain speed rating, we need to understand why we might need a tire with a specific speed raging for our vehicle. The answer is that the manufacturer of the vehicle, when engineering that car or truck, decided that it needs tires rated for that speed, even though you’ll never drive that fast.

McKenney explained that generally—he stressed that’s it’s not always the case—but generally, the higher the speed rating, the softer the tire compound, and the more grip the tire has to offer.

Why is it important? Added grip means the tire will stop faster, turn more precisely, and accelerate better with less slippage. All that translates into better performance, better handling, and that’s the reason manufacturers want you to replace the tires on your vehicle with ones that offer the same speed rating. As insane as that speed may be, it has nothing to do with the speeds you’ll actually drive, and everything to do with the way they designed your car to handle on the road.

So don’t think of speed ratings as having anything to do with the speed you’ll be driving. Instead, think of the speed rating as an indicator of the performance of the tire, and how that translates into better handling and improved safety for your vehicle.